Air filter



FIG. 1 is a perspective view of an air filter showing our new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The dash dot line immediately adjacent to the claimed area in FIG. 6 represents the boundaries of the claimed design. The dashed lines in the figures illustrate the portions of the design that form no part of the claimed design. None of the broken lines form any part of the claimed design. 

CLAIM We claim the ornamental design for an air filter, as shown and described. 